Angie's List charges homeowners to see the listings of good contractors.

Then Angie's calls up the contractors and tells them that they won't be highly visible on the reports unless they pay Angie's.

So even though I've been an A+ plumbing contractor on Angie's for years, you are unlikely to see me on their search. You will most likely see those contractors with a large advertising budget, like Yellow Pages.
You would think that paying Angie's would get you a list of the better contractors, but in reality, you still see the contractors that are paying the most money for leads.

Then ANYONE can give a negative feedback, regardless of the reason for their displeasure. I had one say I did good work but would not call me back because their job was more involved than what they had indicated over the phone. They, like many people, did NOT hear the part about the "actual cost would depend on what actually had to be done", or my statement when I got there that they "had the larger than normal valve and it would cost more".